Continuous casting



Jan. 14, 1969 N. F. NEUMANN CONTINUOUS CASTING Filed March 11, 1966 IN TOR. NORBERT F. MANN W M 2 fi J E, r E; P: E; 2

ammd 71/1141 72 .6 15

ATTOR N EYS United States Patent 3,421,569 CONTINUOUS CASTING Norbert F. Neumann, Rye, N.Y., assignor to Kennecott Sales Corporation, New York, N.Y., a corporation of New York Filed Mar. 11, 1966, Ser. No. 533,574

U.S. Cl. 164-86 Int. 'Cl. B22d 11/02; B22d 11/12; B22d 19/00 Claim ABSTRACT OF THE DISCLOSURE This invention relates to the continuous casting of metals in graphite molds in which the casting is formed and moved downwardly and has for its object the provision of an improved casting process of this general type.

The process of this invention achieves the production of continuous castings consisting of an exterior tube of one metal surrounding a core of another metal of lower melting point. The dual metal or clad metal castings are produced in accordance with the process of the invention by forming and solidifying a tube of a relatively high melting point metal in a downward direction between a graphite mold and a mandrel and pouring the low melting point metal through the mandrel and into the solidified tube as it moves downwardly, completely filling the interior and forming a solid casting having an exterior tube of one metal and a core of another metal. It is an important aspect of the invention that the selection of metals and the casting conditions be carried out so that there is a minimum of interface dissolving or objectionable alloying of one metal in or with the other. Some interface alloying either by solution or diffusion is not objectionable. The objectives of the invention are achieved by selecting a tube metal which, while hot, has a low rate or capacity for interaction with the core metal which is liquid.

In accordance with the process of the invention, the molten core metal is poured into the downwardly moving tube which is at a temperature considerably below its melting point and the tube is exteriorly cooled to effect the most rapid extraction of heat and cooling of both metals so that the dual metal casting passes through the temperature gradient of reactivity as rapidly as possible. For example, a casting consisting of a copper tube and an aluminum core is an especially effective combination of metals which can be formed by the process of the invention with a minimum of interboundary alloying notwithstanding the fact that these metals have a high degree of mutual solubility when molten.

The process of the invention applies to various metals and the reference herein to metal comprehends and is intended to apply to the metal and the base metal alloys. The invention is applicable to any tube metal, and core metal of lower melting point than the tube metal which, under the conditions aforementioned do not result in such boundary interaction as to form an appreciable amount of a third metal alloy between the tube and the core.

The accompanying drawing illustrates an arrangement of continuous casting apparatus suitable for carrying out a process of the invention in which the figure is a side elevation with parts in section.

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The apparatus illustrated in the drawing comprises a graphite mold 1 provided with any suitable water cooling means 2. The interior wall surface 3 may be round, square, octagonal, or the like, depending on the exterior shape of the casting to be made. It is to be understood the graphite mold is secured in suitable supporting apparatus, preferably provided with vibrating means, as is well known in this art. In the continuous casting of tubes it is necessary to provide a mandrel located centrally of the inner space in the mold to provide the tubular space into which the core metal is poured and solidified. The apparatus for practicing the process of the invention employs a mandrel 4, formed of graphite, or cast iron, located centrally of the inner wall 3. The wall 3 and the mandrel are tapered slightly downwardly to compensate for the shrinkage of the metal tube T as the metal solidifies, and shrinks further as the solid tube cools.

The mandrel has an interior opening 10 with an inlet connection 11 for introducing molten core metal, for example molten aluminum, and a valve seat member 12 secured at the lower end. A vent duct 13 is provided in the mandrel to allow the escape of gas from the space 14 inside the tube. A valve rod member 15 formed of a material inert to the core metal extends from the valve seat 12 to the top and through a close-fitting hole 16 in the top of the mandrel. As in the usual continuous casting operations the cast tube is engaged by a pair of power driven pinch rollers 17 which pull the casting downward at a rate synchronized with the rate of feed of molten metal.

In carrying out an operation of the invention a ladle or other vessel provided with means to pour the metal at a controlled rate (not shown) is located near the mold 1 so that the metal poured into the annular space between the mold and the mandrel will maintain the surface of liquid metal, for example at 20. This metal for forming the tube T is the relatively high temperature metal such as iron, copper, nickel, aluminum or the like. The rate of feed of molten metal and the rate of tube withdrawal are such that the metal below the area 21 is solid. It is usually necessary to spray the solid tube with cooling water as by means of nozzles N before it is engaged by the pull rollers 17.

The core forming metal C is passed into the mandrel interior 10 which is preferably maintained filled with this metal. By means of a suitable control mechanism (not shown) which raises and lowers the rod 15 to throttle the rate of flow of core metal, a level of liquid metal is maintained at 22. This control apparatus may be operated in response to radiation through the core metal at the liquid level 22 by means of the radiation sensing means 23. The tube T is cooled by water sprays from nozzles N where the liquid core metal enters to speed its solidification and shorten the time the liquid metal is in contact with the tube T.

This core metal may be aluminum cast into a copper tube or sodium cast into a copper or aluminum tube. Any core metal may be used such as aluminum, magnesium, lead, sodium and the like provided it is compatible with the metal of the tube.

The castings consisting of a tube and a core have many important uses. They may be forged as in a swaging operation to form rods, drawn through dies to form clad wire, punched and rolled into pipe, or rolled flat to form clad sheets or strips and the like.

I claim:

1. The continuous casting process which comprises passing molten copper into an annular mold space, cooling said annular space to solidify said molten copper into a hollow tube, spraying the outer surface of said hollow tube with water to further cool the hollow tube,

passing the hollow tube through a pair of pinch rollers to pull the tube downward, passing molten aluminum through a control member into the center of the hollow tube, sensing the level of the molten aluminum with radiation sensing means to regulate said control member whereby the level of molten aluminum is maintained at the position of the sensing means, and spraying the outer surface of the tube with Water to extract heat from the aluminum and increase its rate of solidification.

FOREIGN PATENTS 7/1952 Germany. 10/ 1962 Germany.

4/ 1957 France.

J. SPENCER OVERHOLSER, Primary Examiner.

V. K. RISING, Assistant Examiner.

U.S. C1. X.R. 

